CN106255222B

CN106255222B - Wireless communication system, UE information transmitting method and base station information receiving method

Info

Publication number: CN106255222B
Application number: CN201610384457.6A
Authority: CN
Inventors: 李骁昣; 金荣石; 郭度荣
Original assignee: Kt Co
Current assignee: Kt Co
Priority date: 2015-06-15
Filing date: 2016-06-02
Publication date: 2019-12-27
Anticipated expiration: 2036-06-02
Also published as: US10097251B2; CN106255222A; US20160365957A1

Abstract

The present invention provides a wireless communication system, comprising: two or more remote units; and a digital unit configured to connect one remote unit having the maximum number of antennas to one output port or connect two or more remote units having a number of antennas lower than the maximum number of antennas to one output port.

Description

Wireless communication system, UE information transmitting method and base station information receiving method

Cross Reference to Related Applications

This application claims 2015 priority from korean patent applications 10-2015-0084126 and 10-2015-0098130, filed on 15 th and 10 th of 2015, which are incorporated herein by reference for all purposes as if fully set forth herein.

Technical Field

The present invention relates to a technique for transmitting downlink data. The present invention relates to a technique for simultaneously transmitting downlink data to a plurality of User Equipments (UEs) using the same time/frequency resources by a base station (i.e., eNB) supporting downlink data transmission through a plurality of transmit antennas.

Background

An eNB supporting downlink data transmission through multiple transmit antennas simultaneously transmits downlink data to multiple UEs using the same time/frequency resources.

In particular, a case in which a specific eNB apparatus performs downlink data transmission for one spatial region using a plurality of transmit antennas together may be supported, and a case in which a plurality of transmit antennas are distributed to perform downlink data transmission for respective spatial regions may also be supported.

At this time, the UE is required to generate and report information capable of discriminating an environment supporting the following cases: in this case, a plurality of transmission antennas are distributed, and the eNB performs downlink data transmission for each spatial region.

Disclosure of Invention

In one aspect, the present invention provides a wireless communication system comprising two or more remote units and a digital unit configured to connect one remote unit having a maximum number of antennas to one output port or connect two or more remote units having a number of antennas lower than the maximum number of antennas to one output port.

The digital unit is configured to support data services for two or more cell areas formed by each of the two or more remote units.

The digital unit receives information for identifying a cell area including a specific User Equipment (UE) therein, belonging to one of two or more cell areas, from the specific UE.

In another aspect, the present invention provides a method of transmitting information of a User Equipment (UE), including: receiving a CSI-RS; generating antenna port information for dividing antenna ports through the received CSI-RS; and transmitting the antenna port information.

In another aspect, the present invention provides a method of receiving information of a base station, the method including transmitting a CSI-RS; receiving antenna port information for dividing antenna ports from a User Equipment (UE); and dividing a region in which the UE is included by the antenna port information, individually scheduling the UEs included in the region, and performing data transmission.

In another aspect, a User Equipment (UE) is provided. The UE includes: a communication unit configured to receive a CSI-RS; and a control unit configured to generate antenna port information dividing antenna ports through the received CSI-RS. The communication unit transmits antenna port information.

In another aspect, the present invention provides a base station. The base station includes: a communication unit configured to transmit CSI-RS and configured to receive antenna port information for dividing antenna ports from a User Equipment (UE); and a control unit configured to divide an area in which the UE is included by the antenna port information, to individually schedule the UEs included in the area, and to perform data transmission.

In another aspect, the present invention provides a method of receiving base station information, the method including: receiving an uplink signal from a User Equipment (UE); and dividing a region in which the UE is included by identifying whether the uplink signal is received from a specific antenna port, and performing data transmission by individually scheduling the UEs included in the region.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

fig. 1 is a configuration diagram of a wireless communication system employing an embodiment;

fig. 2 illustrates time and frequency resources in an LTE system/LTE-advanced system;

fig. 3 illustrates radio resources of 1 subframe and 1 RB, which are the minimum unit for downlink scheduling in an LTE system/LTE-advanced system;

fig. 4 illustrates an example of a structure of a wireless communication system for providing data services to respective cell areas;

fig. 5 illustrates an example of a wireless communication system structure according to an embodiment;

fig. 6 illustrates another example of a wireless communication system structure according to another embodiment;

fig. 7 illustrates another example of a wireless communication system structure according to another embodiment;

fig. 8 is a flowchart of a method of transmitting and receiving information of a UE and an eNB according to another embodiment;

fig. 9 illustrates an example of timing when reporting a Port Indicator (PI);

fig. 10 illustrates an operational flow diagram of a UE according to another embodiment;

fig. 11 illustrates an operational flow diagram of an eNB according to another embodiment;

fig. 12 illustrates a device diagram of a UE according to another embodiment; and

fig. 13 illustrates a device diagram of an eNB according to another embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. When a reference numeral is added to an element in each figure, the same reference numeral is assigned to the same element (even if it is shown in a different figure), if possible. In addition, in the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Fig. 1 is a configuration diagram of a wireless communication system employing an embodiment.

The wireless communication system 100 may be widely installed to provide various communication services such as voice service, packet data, and the like.

The wireless communication system 100 may include a User Equipment (UE)120 and a base station (BS or eNB) 110. Throughout the specification, the user equipment 120 may be an inclusive concept representing a user terminal used in wireless communication, including a UE (user equipment) in WCDMA, LTE, HSPA, etc., and an MS (mobile station), UT (user terminal), SS (subscriber station), wireless device, etc., in GSM.

A base station 110 may generally refer to a station that performs communication with User Equipment (UE), and may also be referred to as a Node B (Node-B), an evolved Node B (enb), a sector, a station, a Base Transceiver System (BTS), an access point, a relay Node, a Remote Radio Head (RRH), a Radio Unit (RU), a small cell, and so on.

In this specification, the cell 130 may be understood as an inclusive concept that represents a part of an area covered by a BSC (base station controller) in CDMA, a NodeB in WCDMA, an eNB or a sector (site) in LTE, or the like, and this concept may include various coverage areas such as a communication range of a megacell, a macrocell, a microcell, a picocell, a femtocell, a relay node, and the like.

Each of the above-mentioned respective cells 130 has a base station controlling the corresponding cell, and thus the base station can be understood in two ways: i) the base station may be the device itself that provides the megacells, macrocells, microcells, picocells, femtocells, and microcells associated with the wireless area, or ii) the base station may refer to the wireless area itself. In the manner i), all devices that interact with each other so that a predetermined wireless area is provided can be controlled by the same entity or cooperatively configure the wireless area can be represented as a base station. The eNB, RRH, antenna, RU, Low Power Node (LPN), point, transmission/reception point, transmission point, reception point, etc. may be an embodiment of a base station based on a configuration type of a wireless area. In the mode ii), a radio area itself in which a signal is received or transmitted from the viewpoint of a terminal or an adjacent base station can be represented as a base station.

Hereinafter, a macrocell, a microcell, a picocell, a femtocell, a small cell, an RRH, an antenna, an RU, an LPN, a point, an eNB, a transmission/reception point, a transmission point, and a reception point may be generally referred to as a base station 110.

In this specification, the user equipment 120 and the base station 110 are used as two inclusionary transceiving objects to implement the technology and technical concept described in this specification, and it may not be limited to predetermined terms or words. In this specification, the user equipment 120 and the base station 110 are used as two (uplink or downlink) inclusionary transceiving objects to implement the technology and technical concept described in this specification, and it may not be limited to predetermined terms or words. Here, Uplink (UL) refers to a scheme in which data transmission and reception are performed by the user equipment 120 with respect to the base station 110, and Downlink (DL) refers to a scheme in which data transmission and reception are performed by the base station 110 with respect to the user equipment 120.

There is no limitation on the multiple access technique to be applied to the wireless communication system 100. Various multiple access schemes may be used, such as CDMA (code division multiple Access), TDMA (time division multiple Access), FDMA (frequency division multiple Access), OFDMA (orthogonal frequency division multiple Access), OFDM-FDMA, OFDM-TDMA, OFDM-CDMA, and so forth. Embodiments of the present invention may be applicable to resource allocation in asynchronous wireless communication schemes evolved into LTE and LTE-advanced through GSM, WCDMA, and HSPA, and may be applicable to synchronous wireless communication schemes evolved into UMB through CDMA and CDMA-2000. The present invention may not be limited to a specific wireless communication field and may include all technical fields to which the technical idea of the present invention may be applied.

The uplink transmission and the downlink transmission may be performed based on a TDD (time division duplex) scheme in which transmission is performed according to different times or based on an FDD (frequency division duplex) scheme in which transmission is performed according to different frequencies.

Further, in systems such as LTE and LTE-advanced (LTE-a), standards may be developed by configuring the uplink and downlink on a single carrier or a pair of carriers. The uplink and downlink may transmit control information through a control channel such as PDCCH (physical downlink control channel), PCFICH (physical control format indicator channel), PHICH (physical hybrid ARQ indicator channel), PUCCH (physical uplink control channel), EPDCCH (enhanced physical downlink control channel), etc., and may be configured as a data channel such as PDSCH (physical downlink shared channel), PUSCH (physical uplink shared channel), etc., thereby transmitting data.

EPDCCH (enhanced PDCCH or extended PDCCH) may be used to send control information.

In this specification, a cell 130 may refer to a coverage of a signal transmitted from a transmission/reception point, a component carrier having a coverage of a signal transmitted from a transmission/reception point (transmission point, or transmission/reception point), or a transmission/reception point itself.

The wireless communication system 100 according to the embodiment refers to a coordinated multi-point transmission/reception (CoMP) system, a coordinated multi-antenna transmission system, or a coordinated multi-cell communication system in which two or more transmission/reception points cooperatively transmit a signal. The CoMP system may include at least two multi-transmission/reception points and a terminal.

The multiple transmission/reception points may be a base station or a macro cell (which is hereinafter referred to as 'eNB') and at least one RRH connected to the eNB through an optical cable or an optical fiber and wiredly controlled, and have high transmission power or low transmission power within a macro cell area.

Hereinafter, downlink refers to a communication or communication path from a multi transmission/reception point to a terminal, and uplink refers to a communication or communication path from a terminal to a multi transmission/reception point. In the downlink, the transmitter may be part of a multiple transmission/reception point, and the receiver may be part of a terminal. In the uplink, the transmitter may be part of a terminal, and the receiver may be part of a multiple transmission/reception point.

Hereinafter, the case of transmitting and receiving a signal through PUCCH, PUSCH, PDCCH, EPDCCH, PDSCH, etc. may be described by the expression "transmitting or receiving PUCCH, PUSCH, PDCCH, EPDCCH, or PDSCH".

In addition, hereinafter, the expression "transmitting or receiving a PDCCH or transmitting or receiving a signal through a PDCCH" includes "transmitting or receiving an EPDCCH or transmitting or receiving a signal through an EPDCCH.

That is, a physical downlink control channel used herein may refer to PDCCH or EPDCCH, and may represent a meaning including both PDCCH and EPDCCH.

In addition, for convenience of description, the EPDCCH corresponding to an embodiment of the present invention may be applied to a portion described using the PDCCH and a portion described using the EPDCCH.

Meanwhile, the upper layer signaling includes RRC signaling transmitting RRC information including RRC parameters.

The base station 110 performs downlink transmission to the UE 120. The base station 110 may transmit a Physical Downlink Shared Channel (PDSCH), which is a main physical channel for unicast transmission, and may transmit a Physical Downlink Control Channel (PDCCH) for transmitting downlink control information, such as scheduling required to receive the PDSCH and scheduling grant information for transmitting an uplink data channel (e.g., a Physical Uplink Shared Channel (PUSCH)). Hereinafter, transmission and reception of signals through each channel will be described as transmission and reception of the corresponding channel.

The mobile communication system 100 has evolved into a high-speed, high-quality wireless packet data communication system to provide data services and multimedia services beyond the early voice-oriented services. Various mobile communication standards such as High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Long Term Evolution (LTE), and long term evolution-advanced (LTE-a) of the 3 rd generation partnership project (3GPP) have been recently developed to support high-speed and high-quality wireless packet data communication services. In particular, the LTE system is a system developed to efficiently support high-speed wireless packet data transmission, which maximizes wireless system capacity by using various radio access technologies. The LTE-a system is a wireless system obtained by improving the LTE system, which has improved data transmission capacity compared to the LTE system.

In general, an LTE system refers to an eNB and a UE corresponding to release 8 or release 9 of the 3GPP standards group. The LTE-advanced system refers to an eNB and a UE corresponding to release 10 of the 3GPP standards group. The 3GPP standards group is developing standards for subsequent releases (after standardization of the LTE-advanced system) with improved performance based on standardization of the LTE-advanced system.

Hereinafter, an LTE/LTE-advanced system will be taken as an example of the wireless communication system described with reference to fig. 1, but the present invention is not limited thereto.

The LTE/LTE-advanced system employs multiple-input multiple-output (MIMO) and Orthogonal Frequency Division Multiple Access (OFDMA) techniques and well utilizes the advantages of each technique.

First, MIMO in which wireless signals are transmitted using a plurality of transmission antennas may be classified into single-user MIMO (SU-MIMO) for transmitting to one UE and multi-user MIMO (MU-MIMO) for transmitting data to a plurality of UEs using the same time/frequency resources.

In the case of SU-MIMO, the multiple transmit antennas transmit wireless signals to multiple spatial layers for one receiver. At this time, the receiver needs to be equipped with a plurality of receiving antennas in order to support the plurality of spatial layers.

Conversely, in the case of MU-MIMO, the plurality of transmit antennas transmit wireless signals to a plurality of spatial layers of the plurality of receivers. MU-MIMO is more advantageous than SU-MIMO because MU-MIMO does not require a receiver equipped with multiple receive antennas. However, as a disadvantage, mutual interference may be generated between wireless signals for different receivers, since the wireless signals are transmitted for the plurality of receivers with the same frequency and time resources.

One of the main factors that can achieve capacity increase by the OFDMA method is: scheduling performance of different UEs on the frequency axis. That is, like the characteristic that the channel changes according to time, when the characteristic that the channel changes according to frequency is additionally used, the characteristic is combined with an appropriate scheduling method, and thus a higher capacity gain can be obtained.

Fig. 2 illustrates time and frequency resources in an LTE/LTE-advanced system.

Referring to fig. 1 and 2, radio resources transmitted from an eNB 110 to a UE 120 are divided in units of Resource Blocks (RBs) 220 on a frequency axis and in units of subframes 210 on a time axis. In an LTE/LTE-advanced system, a resource block 220 typically includes 12 subcarriers and occupies a bandwidth of 180 kHz. In contrast, in an LTE/LTE-advanced system, a subframe 210 generally includes 14 OFDM symbol sections and occupies a period of 1msec (millisecond). In performing scheduling, the LTE/LTE-advanced system may allocate resources in units of subframes 210 on a time axis and may allocate resources in units of resource blocks 220 on a frequency axis.

Fig. 3 illustrates radio resources of 1 subframe and 1 RB, which is a minimum unit for downlink scheduling in an LTE/LTE-advanced system.

Referring to fig. 3, a downlink scheduling unit of the LTE/LTE-advanced system includes one subframe 310 on a time axis and includes one RB 320 on a frequency axis. The radio resource is formed of 12 subcarriers in the frequency domain and 14 OFDM symbols in the time domain, and thus may have a total of 168 unique frequency and time positions. In an LTE/LTE-advanced system, each unique frequency and time position of fig. 3 is referred to as a Resource Element (RE). In addition, one subframe 310 is configured with two slots, each of which is configured with seven OFDM symbols.

Several different types of signals may be transmitted in the radio resource shown in fig. 3.

1. Cell-specific reference signal (CRS) 330: a reference signal transmitted for channel measurement of all UEs belongs to a specific cell;

2. demodulation reference signals (DMRS)340 and 341: a reference signal transmitted for data decoding of a specific UE;

3. physical Downlink Shared Channel (PDSCH) 350: a data channel transmitted in downlink, the eNB transmits data to the UE using the PDSCH, and transmits the PDSCH using REs in which the reference signal is not transmitted in the data region of fig. 3;

4. channel state information reference signal (CSI-RS) 370: the CSI-RS is a reference signal transmitted to a UE belonging to a specific signal transmission point and is used to measure a channel state. A plurality of transmission points may be included in one cell, and thus a plurality of CSI-RSs may be transmitted in one cell;

5. other control channels 360 (e.g., PDCCH, PCFICH, and PHICH): the other control channel 360 transmits control information necessary for receiving the PDSCH by the UE or transmits ACK/NACK for uplink HARQ operation.

In addition to these signals, the LTE-advanced system may configure muting such that CSI-RS 370 transmitted by another eNB is received by the UE of the respective cell without interference. The muting may be employed at locations where CSI-RS 370 may be transmitted. Generally, the UE skips a corresponding radio resource and receives a data signal. In LTE-advanced systems, muting is also referred to as zero-power CSI-RS as another term. The reason is that muting is applied to the position of the CSI-RS 370 and no signal is transmitted because the transmission power is zero.

Depending on the number of antennas transmitting CSI-RS 370, some of the positions labeled A, B, C, D, E, F, G, H, I and J may be used to transmit CSI-RS 370. In addition, some of the positions labeled A, B, C, D, E, F, G, H, I and J may be used to implement silencing. The number of antenna ports supported in the LTE-advanced system is two, four, and eight. The CSI-RS 370 may be transmitted using two, four, and eight REs for each antenna port. When the number of antenna ports is two, the CSI-RS 370 is transmitted to half of the specific pattern in fig. 3. When the number of antenna ports is four, in fig. 3, the CSI-RS 370 is transmitted to the entire specific pattern. When the number of antenna ports is eight, in fig. 3, the CSI-RS 370 is transmitted using two consecutive patterns. Instead, the silence is formed in a pattern unit.

As described above, the LTE/LTE-advanced system utilizes the MIMO technology that transmits data using a plurality of transmission/reception antennas to increase a data transmission rate and a system capacity. Up to now, the LTE-advanced system supports up to eight antenna ports per UE and supports transmission of up to eight spatial layers at a time.

The UE 120 connected to the corresponding specific eNB 110 measures a downlink channel using the CSI-RS 370 and reports channel information on the downlink channel to the eNB, so that the specific eNB 110 performs UE scheduling for a given time/frequency resource and determines a precoding method applied to the plurality of antennas. The LTE/LTE-advanced system uses the following three pieces of channel state information or channel feedback information (hereinafter referred to as 'channel state information').

● Rank Indicator (RI): information on the number of spatial layers preferred by the UE

● Precoding Matrix Indicator (PMI): information on index of precoding matrix preferred by UE given most recently reported RI

● Channel Quality Indicator (CQI): information on maximum Modulation and Coding Scheme (MCS) level satisfying Block error Rate (BLER)0.1 given most recently reported RI/PMI

For detailed RI/PMI/CQI definition and reporting period, refer to 3GPP standard document [ 3GPP TS 36.213 ].

The wireless communication system described with reference to fig. 1 may be implemented in various ways. Hereinafter, examples of the wireless communication system are described in detail with reference to fig. 4 to 7.

Fig. 4 illustrates an example of a structure of a wireless communication system for providing data services to respective cell areas.

Referring to fig. 4, in a system in which a Digital Unit (DU)400 is separated from two or more Remote Units (RUs) 410 to 440, at least one of the RUs 410 to 440 is directly connected to the DU 400.

The DU 400 is a device for performing most operations of the eNB. Each output port 401 of the DU 400 is connected to RUs 410 to 440 that actually perform wireless data transmission. Generally, a function corresponding to each output port 401 of the DU 400 is performed to perform all functions performed by one eNB and functions of the connected RUs 410 to 440. In the case of the LTE/LTE-advanced system, the functions of all enbs shown in the 3GPP standard document [ 3GPP TS 36.300 ] correspond to the functions corresponding to each output port 401.

Here, each of the RUs 410 to 440 should actually be installed in a corresponding cell area to actually transmit data to the UE. However, it is not necessary to actually install the DUs 400 connected to the respective RUs 410-440 in a cell area. The DU 400 connected to each RU 410 to 440 may be installed in a separate space, and may be connected to the RUs 410 to 440.

In addition, the RUs 410 to 440 are connected to at least one antenna port. The number of antenna ports shown in fig. 4 represents the number of ports of the CSI-RS for the LTE-a system. The LTE-advanced system is designed to give CSI-RS port numbers starting with number 15 and allocate up to eight ports up to number 22. In the case of fig. 4, the DU 400 has four output ports 401 and is thus connected to four RUs 410 to 440. Each of the RUs 410-440 has one or more antennas and transmits data to a particular cell region.

As described above, when one DU 400 provides data services to respective cell areas, in general, different output ports 401 are used for data services of different areas, and each of the RUs 410 through 440 connected to each output port 401 forms a cell, thus providing the data services to UEs included in the corresponding cell.

That is, in general, when one DU 400 provides data services to four areas, the corresponding DU 400 should include four output ports, each of which is connected to a specific RU, so that the data services can be provided to the corresponding area.

As shown in fig. 4, it is assumed that four output ports 401 are connected to a first RU 410, a second RU 420, a third RU 430, and a fourth RU 440, respectively, and that each of the RUs 410 to 440 provides data services for an Area1, an Area 2, an Area3, and an Area 4. In addition, it is assumed that Area1 is a very large space and thus the number of connected UEs is large, Area 2 is smaller than Area1 and thus the number of connected UEs is smaller than the number of connected UEs of Area 1Area1, and Area3 and Area 4are a very small space and thus the number of connected UEs is very small.

In general, when MIMO technology using different antennas is used, complexity of the DU 400 increases, but data service can be provided to a wider area. Therefore, it is assumed that the Area1 uses four antenna ports, the Area 2 uses two antenna ports, and the Area3 and the Area 4 use only one antenna port.

In general, since the total calculation capacity and the resource capacity of the DU 400 are to be designed assuming that the maximum number of antennas supported by each of all the output ports 401 is used, the total calculation capacity and the resource capacity cannot be used in the case of fig. 4. That is, since the DU 400 shown in fig. 4 has a calculation capacity and a resource capacity capable of using up to four antennas in all the output ports 401, the capacity of the usable DU 400 reaches a maximum value in the Area 1. However, in areas Area 2, Area3, and Area 4, the capacity of DU 400 cannot be fully utilized due to the small number of antennas.

In the case where one DU 400 provides data services to respective areas, as shown in fig. 4, the conventional wireless communication system structure in which each of the plurality of RUs 410 to 440 connected to one DU 400 has a different number of antennas and uses output ports of different DUs has the following disadvantages: wherein the capacity of the DUs cannot be fully utilized as described above.

The following embodiments provide a method of performing a channel feedback operation of an eNB and related UE to overcome a disadvantage that a capacity of a DU cannot be fully utilized due to different numbers of antennas used for respective areas providing wireless communication services for the DU supporting the multiple antennas, as described with reference to fig. 4.

The embodiments described below consider the following: wherein the specific DU supports data services for a plurality of cell areas using a plurality of antennas. In the embodiments described below, even in the case where each small cell region served by a particular DU receives data transmission through an RU having a different number of antennas, the entire capacity of the DU can be fully utilized.

That is, one RU having the largest number of antennas may be connected to one DU output port. However, after a plurality of RUs having a number of antennas smaller than the maximum number of antennas are connected to one DU output port, a feedback operation is performed so that the DU can know the type of RU connected to a specific UE belonging to one of the plurality of cell areas. Thus, the capacity of the DU can be fully utilized.

Fig. 5 illustrates an example of a wireless communication system structure according to an embodiment.

Referring to fig. 5, in a wireless communication system structure according to an embodiment, in a system in which a Digital Unit (DU)500 and one or more Remote Units (RUs) 510 to 540 are divided, at least one of the RUs 510 to 540 is directly connected to one DU 500.

One RU 510 having many antennas may be connected to one output port 501 of a specific DU 500. Alternatively, the plurality of RUs 520, 530, and 540 with a small number of antennas may be connected to another output port 502.

That is, referring to fig. 5, one first RU 510 having four antennas is connected to the first output port 501 of the DU 500, and a second RU 520 having two antennas, a third RU 530 having one antenna, and a fourth RU 540 having one antenna are all connected to the second output port 502.

As shown in fig. 5, when the plurality of RUs 520, 530, and 540 share the same second output port 502, there is an advantage in that the capacity of the DU can be fully utilized, which is different from the conventional wireless communication system structure shown in fig. 4.

It is assumed that, among signals for all Antenna Ports (APs) 15, 16, 17, and 18 output from the second output port 502 of the DU 500, the second RU 520 connects only a signal for the APs 15 and 16 to each of two antennas to use the signal for the APs 15 and 16, the third RU 530 connects only a signal for the AP17 to one antenna to use the signal for the AP17, and the fourth RU 540 connects only a signal for the AP18 to one antenna to use the signal for the AP 18.

However, the present invention is not limited thereto. The present invention contemplates the use of a separate signal distributor 603 that distributes the signals output from the DUs for all of the APs 15, 16, 17 and 18 to transmit the signals to the respective RUs, as shown in fig. 6.

Fig. 6 illustrates another example of a wireless communication system structure according to another embodiment.

Referring to fig. 6, a wireless communication system architecture may include a signal distributor 603 according to another embodiment. Among the signals output from the second output port 602, the signal distributor 603 may transmit signals corresponding to the APs 15 and 16 to the second RU620, may transmit a signal corresponding to the AP17 to the third RU 630, and may transmit a signal corresponding to the AP18 to the fourth RU 640. Accordingly, the plurality of RUs 620, 630, and 640 may be connected to one second output port 602.

Fig. 7 illustrates another example of a wireless communication system structure according to another embodiment.

As shown in fig. 7, in a wireless communication system structure according to another embodiment, one second RU720, which can support four APs, can allocate and install APs to support respective areas. That is, antennas corresponding to APs 15 and 16 of the second RU720 may be installed in Area 2, an antenna corresponding to AP17 may be installed in Area 3Area3, and an antenna corresponding to AP18 may be installed in Area 4. Accordingly, the AP output from one RU720 can support each region.

All wireless communication systems according to the embodiments shown in fig. 5, 6 and 7 show the wireless communication system structure for DUs 500, 600 and 700 that support up to four APs. However, the present invention is not limited thereto, and naturally extends to the case where the number of antennas is larger. For example, in case that the DU supports up to eight APs, all eight antennas may be used for one area. Alternatively, one, two or four antennas may be distributed and installed to support the area.

From the perspective of the DU, all wireless communication system structures according to the embodiments shown in fig. 5, 6 and 7 may be considered to be the same case, and the UEs belong to areas 1, 2, 3 and 4Area 1, Area 2, Area3 and Area 4 because only the method of connection from the DU to each AP is different. That is, the case of the wireless communication system according to the embodiments shown in fig. 5, 6, and 7 is the following case: wherein the output port of a specific DU provides a data service to UEs belonging to Area1 using the APs 15, 16, 17 and 18, the APs 15 and 16 for another output port provide a data service to UEs belonging to second Area 2, the AP17 provides a data service to UEs belonging to third Area3, and the AP18 provides a data service to UEs belonging to fourth Area 4.

In the case of the wireless communication system according to the embodiments shown in fig. 5, 6, and 7, when the DU can identify an area in which a specific UE is included, overall system performance can be increased. If each region is sufficiently spatially divided, resources can be reused in each region since UEs belonging to different regions do not generate mutual interference even if receiving data simultaneously within the same time and frequency regions. That is, the eNB may receive downlink channel feedback of the UE or may measure uplink signals of the UE. Accordingly, the eNB may identify an area in which the UE is included. Thus, the overall system capacity may be increased.

A first method for enabling an eNB to identify an area to which a UE belongs among areas divided only by an AP includes: receiving an uplink signal transmitted from the UE; identifying whether a signal is received only from a specific AP; determining that the UE belongs to an area divided by an AP in which a corresponding signal is received; and performing UE scheduling. Here, the uplink signal may be some of an initial access signal, a sounding reference signal, a control signal, and a data signal of the UE.

For example, in case of the wireless communication system according to the embodiment shown in fig. 5, the second output port 502 of the DU 500 serving the areas 2, 3, and 4 may measure the strength of an uplink signal of a specific UE, which may be performed according to each AP. When the uplink signal is mostly (i.e., equal to or greater than a certain critical value) received by the AP15 and the AP16, the second output port 502 determines that the UE belongs to the area 2. When the uplink signal is mostly received only by the AP17, the second output port 502 determines that the UE belongs to the area 3. When the uplink signal is largely received only by the AP18, the second output port 502 determines that the UE belongs to the area 4. Accordingly, scheduling may be performed separately for UEs belonging to different regions. Thus, overall system performance enhancement may be achieved.

In case of the wireless communication system, according to the embodiments shown in fig. 6 and 7, as such, the eNB may receive an uplink signal transmitted from the UE, may identify an AP receiving the signal, may determine that the UE belongs to an area divided by the AP receiving the corresponding signal, and may perform UE scheduling.

The method of receiving information of an eNB according to another embodiment may include: a reception step for receiving an uplink signal from the UE; and a scheduling step of identifying whether an uplink signal is received by a specific AP to divide an area to which the UE belongs, scheduling the UEs belonging to the area individually, and performing data transmission. As another method, region 1, and regions 2, 3, and 4 using different APs may operate as different cells or may be divided using different CSI-RSs. Accordingly, with respect to the existing LTE-advanced UE, the DU can easily identify an area in which the corresponding LTE-advanced UE is included from among the area1 and the areas 2, 3, and 4. However, in the case of the wireless communication system according to the embodiments shown in fig. 5, 6 and 7, since the areas 2, 3 and 4are divided only by different APs connected to the same output port, it is difficult for the DU to identify a location in which the UE is included among the corresponding areas using feedback information of the existing LTE-advanced UE.

Fig. 8 is a flowchart of a method of transmitting and receiving information of a UE and an eNB according to another embodiment.

Referring to fig. 8, an eNB and a UE transmit and receive information in a wireless communication system. At this time, the wireless communication system structure configuring the eNB may be the wireless communication system described with reference to fig. 5 to 7. As shown in fig. 5 to 7, the wireless communication system structure may be a wireless communication system in which one output port of a DU is connected to two or more RUs as shown in fig. 5 to 7, and may be a wireless communication system in which one output port is connected to only one RU as shown in fig. 4.

The DU and RU described with reference to fig. 5 to 7 may perform the role of the eNB.

First, the eNB transmits a CSI-RS and the UE receives the CSI-RS (S810).

Next, the UE generates antenna port information for dividing antenna ports through the received CSI-RS (S820).

Next, the UE transmits antenna port information and the eNB receives the antenna port information.

Next, the eNB divides a region in which the UE is included by the received antenna port information and individually schedules the UEs included in the region (S840). Next, the eNB transmits data to the UE according to the scheduling (S850).

At this time, the antenna port information may be included in the channel state information or may be included in a newly defined port indicator (or port index) and may be transmitted. The channel state information may be a Precoding Matrix Index (PMI).

Meanwhile, when the number of APs is N, all possible combinations (log) of dividing one, two, or N APs may be generated₂N +1) bits of antenna port information.

When the number of APs is N, antenna port information of a specific bit that divides only some of all possible combinations of one, two, or N APs may be generated.

When the antenna port information is included in the port information, the port information may be transmitted at a time equal to that of the channel state information or transmitted within a period corresponding to an integer multiple of a rank index, which is one of the channel state information.

Hereinafter, transmitting antenna port information through a precoding matrix index, which is one of channel state information, is described in detail. Since the antenna port information is transmitted through the precoding matrix index, a first method of reporting a region in which the UE is located among regions divided only by the antenna ports is to add information for dividing the corresponding antenna ports to precoding matrix information (which may be, for example, the precoding matrix index) reported by the UE.

For example, in the case of the wireless communication system described with reference to fig. 5 to 7, when the UE receives CSI-RSs for four APs and reports [1,1,0,0] as a preferred precoding matrix in response to the CSI-RSs, the eNB may confirm that the UE belongs to area 2. Conversely, in the corresponding case, when the UE reports [0,0,1,0] as the preferred precoding matrix, the eNB may confirm that the UE belongs to region 3.

To express the conventional case, consider a case in which an output port of a specific DU supports N APs and a specific UE receives a CSI-RS having N APs.

Therefore, when the DU adds N precoding matrices { [1,0,0, …,0], [0,1,0, …,0], [0,0,1, …,0], …, [0,0,0, …,1] } to a set of precoding matrices selectable by the UE to divide an area formed by only one AP, the DU can identify an AP to which the UE belongs among the N APs through a PMI reported from the UE.

In addition, in order to divide an area formed by only two APs, the following (N-1) × 4 precoding matrices are added:

{[1,1,0,…,0],[1,-1,0,…,0],[1,j,0,…,0],[1,-j,0,…,0],[0,1,1,…,0],[0,1,-1,…,0],[0,1,j,…,0],[0,1,-j,…,0],…,[0,0,…,1,1],[0,0,…,1,-1],[0,0,…,1,j],[0,0,…,1,-j]}

among the (N-1) × 4 precoding matrices, the first four indicate that the UE belongs to a region formed of only the first and second CSI-RS APs, and each of the four includes actual precoding matrix information applied to the respective first and second CSI-RS APs.

When the DU receives the above-added precoding matrix through the RU, the DU can separately divide UEs identified as belonging to different regions, can perform scheduling, and can reuse resources according to each region.

Hereinafter, transmission antenna port information is described. Here, the antenna port information is included in a newly defined port indicator (or port index) and transmitted.

A second method for increasing frequency efficiency, in which, among areas (e.g., area 2, area3, and area 4 of fig. 5, 6, and 7) divided only by an AP, a UE reports an area to which the UE belongs and a DU uses this information to perform scheduling; the method enables the DU to reuse resources according to each region by performing scheduling after dividing UEs included in individual regions when the UEs report port information (or Port Indicator (PI)) about an AP that is preferably used among all APs to the DU through the RU.

That is, in the wireless communication system shown in fig. 7, when CSI-RS signals are detected only in the AP15 and the AP16, since the UE belongs to the area 2, although the UE receives CSI-RS having four APs (AP 15, AP16, AP17, and AP 18), the UE may report separate feedback information including antenna port information to the eNB.

With respect to a UE receiving a CSI-RS having four APs, the port information (which may report an area divided only by the APs) may include three bits representing the following eight cases.

1. The case where only one AP is identified: { AP15}, { AP16}, { AP17}, and { AP18}

2. The case where only two APs are identified: { AP15, AP16}, { AP16, AP17}, { AP17, AP18}

3. The case where all APs are identified: { AP15, AP16, AP17, AP18}

That is, after the UE is configured to receive the CSI-RS having four APs and feed back information on a preferred AP, when the UE performs feedback using three-bit port information to inform a case among the above eight cases, the UE may divide an area to which the UE belongs, may perform separate scheduling, and thus may increase the capacity of the overall system.

In a similar manner, when the UE is configured to receive the CSI-RS having eight APs { AP15, AP16, …, AP22} and feed back port information on a preferred AP, information enabling the UE to report an area divided only by the APs may include four bits representing the following 16 cases.

1. Where the case of only one AP is seen: { AP15}, { AP16}, …, { AP22}

2. Where the case of only two APs is seen: { AP15, AP16}, { AP16, AP17}, …, { AP21, AP22}

3. Where the case of all APs is seen: { AP15, AP16, …, AP22}

Thus, the four-bit information considers three cases where one, two, or all eight of the regions are used. If a case is added where four APs are seen, the port indicator is increased to five bits.

If the port information is extended to N APs, which are normal values, and one specific area may be formed of one, two, or N APs, a port indicator enabling the UE to report an area divided only by the APs may be defined by (log)₂N +1) bit information.

As another method, when the number of separately configurable maximum areas is reduced by using a single AP or two APs with respect to N APs, the corresponding information may maintain a fixed number of bits or more. For example, when the probability of the area formed by one AP is limited to eight types and the probability of the area formed by only two APs is limited to seven types, all cases (i.e., 4-bit port indicators) can be represented by 16 types, as in the case where it is configured to receive eight CSI-RSs and perform feedback to transmit information on a preferred AP, which is the above example:

1. the case where only one AP is seen: { AP15}, { AP16}, { AP17}, …, { AP22}

2 case where only two APs are seen: { AP15, AP16}, { AP16, AP17}, …, { AP21, AP22}

3. Where the case of all APs is seen: { AP15, AP16, …, AP (N +14) }

In a similar manner, when the probability of a region formed by one AP is limited to four types and the probability of a region formed by two APs is limited to three types with respect to N APs, all cases can be represented by the following eight types (i.e., three-bit port indicators):

1. where the case of only one AP is seen: { AP15}, { AP16}, { AP17}, and { AP18}

2. Where the case of only two APs is seen: { AP15, AP16}, { AP16, AP17}, { AP17, AP18}

3. Where the case of all APs is seen: { AP15, AP16, …, AP (N +14) }

When information of a region where a UE is located among regions where reporting by the UE is divided only by an AP is referred to as a Port Indicator (PI), the corresponding information may be reported at a time equal to that of RI/PMI/CQI and RI/PMI/CQI defined in the existing LTE. As another method, the respective information may be reported at individual times in a period corresponding to an integer multiple of the period in which the RI is reported.

Fig. 9 illustrates an example of timing when reporting a Port Indicator (PI).

Referring to fig. 9, in a feedback mode of RI/PMI/CQI of the existing LTE, PMI/CQI is periodically reported at the same time, and in response to the reporting of PMI/CQI, feedback of RI is performed in a period corresponding to an integer multiple of the period of PMI/CQI. In this case, the PI may be reported at a separate time in a period corresponding to an integer multiple of the period in which the RI is reported. The PI may also be reported at time instants with separate offsets, as in LTE the RI and PMI/CQI are reported at time instants with separate offsets.

Fig. 10 illustrates an operational flow diagram of a UE according to another embodiment.

Referring to fig. 10, in operation 900 for a UE according to an embodiment of another embodiment, the UE receives a CSI-RS configuration and a feedback pattern from an eNB (S910). In step S910, the feedback mode information may include information on whether the UE reports the PMI corresponding to the new precoding matrix or whether the UE reports the PI. In addition, the feedback mode information may include information on a feedback timing.

Next, the UE receives the CSI-RS according to the CSI-RS configuration (S920). In step S920, the UE estimates a channel through the CSI-RS. In addition, in step S920, the UE identifies an area to which the UE belongs through CSI-RS.

Next, the UE generates a PMI in a codebook including a new precoding matrix or generates antenna port information including the above PI (S930).

Next, the UE reports the corresponding antenna port information included in the PMI or PI to the eNB at a given feedback time (S940). Regarding the feedback time, as described with reference to fig. 9, the port information may be transmitted at a time equal to that of the channel state information when the antenna port information is included in the port information, or may be transmitted in a period corresponding to an integer multiple of a Rank Index (RI) which is one of the channel state information.

Fig. 11 illustrates an operational flow diagram of an eNB according to another embodiment.

Referring to fig. 11, in operation 1000 of an eNB according to another embodiment, the eNB transmits CSI-RS configuration and feedback mode information to a UE (S1010). In step S1010, the feedback mode information may include information on whether the UE reports the PMI corresponding to the new precoding matrix or information on whether the UE reports the PI. In addition, the feedback mode information may include information on a feedback timing.

Next, the eNB transmits the CSI-RS according to the CSI-RS configuration (S1020).

Next, the eNB receives antenna port information included in the PMI or the PI (S1030).

Next, the eNB divides the area to which the UE belongs through the PMI or PI and individually schedules the UEs belonging to each area (S1040).

Next, the eNB transmits data to the UE according to the corresponding schedule (S1050).

Fig. 12 illustrates a device diagram of a UE according to another embodiment.

Referring to fig. 12, a UE 1200 includes a communication unit 1210 that receives CSI-RS and transmits antenna port information, and a control unit 1220 that generates antenna port information for dividing antenna ports through the received CSI-RS.

The communication unit 1210 receives a signal, such as a Reference Signal (RS) including a control channel, a data channel, and a CSI-RS of the eNB, and transmits the signal to the control unit 1220. The communication unit 1210 is used to transmit or receive signals, messages or data required to implement the present invention described above to/from the UE.

Control unit 1220 identifies CSI-RS and feedback pattern information from the received signal transmitted from communication unit 1210, and controls the operation of channel estimation and feedback generation. When a specific digital unit required to perform the above-described present invention supports a data service for a plurality of cell areas using a plurality of antennas, the control unit 1220 controls the overall operation of the eNB such that the overall capacity of the digital unit can be sufficiently utilized.

The channel estimation and feedback information generation may be some of the functions of the control unit. Alternatively, there may be additionally a channel estimation unit 1222 and an antenna port information generation unit 1224 for channel estimation and feedback information generation. Channel estimation unit 1222 performs channel estimation according to the CSI-RS transmitted from the eNB. The antenna port information generating unit 1224 generates antenna port information including a PMI or a PI by using the channel estimation information. The generated antenna port information is transmitted to the eNB through the communication unit 1210.

Fig. 13 illustrates a device diagram of an eNB according to another embodiment.

Referring to fig. 13, an eNB 1300 includes a communication unit 1310 that transmits CSI-RS and receives antenna port information dividing antenna ports from a UE; and a control unit 1320 dividing a region to which the UE belongs through the antenna port information, individually scheduling the UEs belonging to the region, and performing data transmission.

The communication unit 1310 transmits signals, such as a control channel, a data channel, and an RS, to the UE, and receives channel state information, etc., from the UE. The communication unit 1310 may transmit and receive downlink control information, data, and messages to and from a base station through a corresponding channel. The communication unit 1310 may be included in some of the RUs shown in fig. 5 to 7.

Control unit 1320 generates CSI-RS configuration information, feedback mode information, scheduling information, and a data channel. The control unit 1320 may be included in some of the DUs shown in fig. 5 to 7. When a specific digital unit required to perform the above-described present invention supports a data service for a plurality of cell areas using a plurality of antennas, the control unit 1320 controls the overall operation of the UE such that the overall capacity of the digital unit can be sufficiently utilized.

The scheduler 1322 may perform scheduling of the UE. The scheduler 1322 may utilize feedback information from the UE to divide an area to which the UE belongs. The scheduler 1322 may generate scheduling information according to the situation. Here, the scheduler may be a function of some control unit. Alternatively, the scheduler may be separate from the control unit.

Further, the communication unit 1310 may receive an uplink signal from the UE. The control unit 1320 may identify whether an uplink signal is received from a specific antenna port to partition an area to which the UE belongs. The control unit 1320 may individually schedule UEs belonging to the area and may perform data transmission.

The UE 1200 described with reference to fig. 12 and the eNB 1300 described with reference to fig. 13 may transmit and receive antenna port information. Here, the antenna port information may be included in the channel state information or may be included in a newly defined port indicator.

At this time, when the antenna port information is included in the port information, the port information may be received at a time equal to that of the channel state information, or may be transmitted and received in a period corresponding to an integer multiple of a rank index, which is one of the channel state information.

According to the above embodiments, a particular digital unit may support data services for multiple cell areas using multiple antennas.

According to the above-described embodiments, even in a case where each cell area served by a specific digital unit receives data transmission through a remote unit having a different number of antennas, the digital unit can fully utilize its entire capacity, and UEs belonging to each cell area can be individually scheduled, thus increasing the capacity of the entire system.

The above description is only for the purpose of illustrating the technical idea of the present invention, and those skilled in the art will recognize that various modifications and variations are possible without departing from the spirit and scope of the present invention. Therefore, the embodiments of the present invention disclosed herein are not described for limiting purposes, and the scope of the technical idea of the present invention is not limited to these embodiments. The scope of the present invention should be understood based on the claims below in such a manner that all technical ideas falling within the scope of equivalents thereof fall within the scope of the present invention.

Claims

1. A wireless communication system, comprising:

a plurality of remote antenna units installed in a plurality of cell areas in a distributed manner and configured to communicate with at least one user equipment, wherein each of the plurality of remote antenna units comprises at least one antenna; and

a digital controller configured to include a plurality of output ports and provide data services for a plurality of cell areas respectively formed by a plurality of remote antenna units through the plurality of output ports,

wherein i) one remote antenna unit having the largest number of antennas among the plurality of remote antenna units is connected to one output port among the plurality of output ports of the digital controller and ii) two or more remote antenna units each having antennas less than the largest number of antennas among the plurality of remote antenna units are connected to share another output port among the plurality of output ports of the digital controller, and

wherein the digital controller i) receives antenna port information for identifying an antenna port supporting a cell area in which the specific user equipment is located among the plurality of cell areas from the specific user equipment, ii) identifies the cell area in which the specific user equipment is located through the received antenna port information, and iii) performs a separate scheduling operation for the specific user equipment located in the identified cell area.

2. The wireless communication system of claim 1, further comprising:

a signal distributor configured to be connected to the digital controller and at least one of the plurality of remote antenna units and configured to distribute a signal transmitted from the digital controller to one of the connected remote antenna units.

3. The wireless communication system of claim 1, wherein at least one of the plurality of remote antenna units is configured with at least two distributively mounted antennas, and

the digital controller is configured to support data services for at least two cell areas formed by the at least two distributed mounted antennas of the remote antenna unit.

4. The wireless communication system of claim 1, wherein the antenna port information is transmitted by being included in a port indicator.

5. A method of a user equipment transmitting information, the method comprising:

receiving a channel state information reference signal from a base station, wherein the base station comprises a plurality of remote antenna units installed in a plurality of cell areas in a distributed manner;

generating antenna port information for identifying an antenna port supporting a cell area in which the user equipment is located, through the received channel state information reference signal; and

transmitting the antenna port information to the base station, wherein the antenna port information is used at the base station to identify the cell area in which the user equipment is located,

wherein the base station i) receives antenna port information for identifying an antenna port supporting a cell area in which the specific user equipment is located among the plurality of cell areas from the specific user equipment, ii) identifies the cell area in which the specific user equipment is located through the received antenna port information, and iii) performs a separate scheduling operation for the specific user equipment located in the identified cell area.

6. The method of claim 5, wherein the antenna port information is transmitted by being included in at least one of channel state information and port information.

7. The method of claim 6, wherein the channel state information is a precoding matrix index and the port information is a port indicator.

8. The method of claim 5, wherein the generating comprises: generating a (log) identifying all possible combinations of 1, 2 or N antenna ports when the number of antenna ports is N₂N +1) bits of antenna port information.

9. The method of claim 5, wherein the generating comprises: when the number of antenna ports is N, specific bit antenna port information for identifying some of all possible combinations of 1, 2, or N antenna ports is generated.

10. The method of claim 6, wherein when the antenna port information is included in the port information, the port information is transmitted at a time equal to that of the channel state information or transmitted in a period corresponding to an integer multiple of a rank index, which is one of the channel state information.

11. A method of a base station receiving information, the method comprising:

configuring the base station to include: i) a plurality of remote antenna units installed in a plurality of cell areas in a distributed manner and configured to communicate with at least one user equipment; and ii) a digital controller configured to include a plurality of output ports and to provide data services through the plurality of output ports for a plurality of cell areas respectively formed by a plurality of remote antenna units;

transmitting a channel state information reference signal to the user equipment;

receiving, by the digital controller, antenna port information for identifying an antenna port supporting a cell area in which the user equipment is located from the user equipment, wherein the antenna port information is generated by the user equipment based on the channel state information reference signal;

the digital controller identifies the cell area in which the user equipment is located through the antenna port information;

the digital controller performing individual scheduling operations for the user equipment located in the identified cell region; and

the digital controller performs data transmission.

12. The method of claim 11, wherein the antenna port information is received by being included in at least one of channel state information and port information.

13. The method of claim 12, wherein the channel state information is a precoding matrix index and the port information is a port indicator.

14. The method of claim 11, wherein the receiving is performedThe method comprises the following steps: receiving a (log) identifying all possible combinations of 1, 2 or N antenna ports when the number of antenna ports is N₂N +1) bits of antenna port information.

15. The method of claim 11, wherein the receiving comprises: when the number of antenna ports is N, specific bits of antenna port information identifying some of all possible combinations of 1, 2, or N antenna ports are received.

16. The method of claim 12, wherein when the antenna port information is included in the port information, the port information is received at a time equal to a time of the channel state information or is received in a period corresponding to an integer multiple of a rank index, which is one of the channel state information.